Conventionally, in an electric apparatus that contains a secondary power supply using a DC-DC (Direct Current to Direct Current) converter, the integrated circuit of the DC-DC converter is often replaced by a plurality of regulators (constant direct current power supply circuits) to reduce costs. In this case, it is difficult to realize power supply by connecting to the output of a plurality of regulators for each one of them. Generally, power supply is realized by using regulators each of which is dedicated to a plurality of power supply areas (e.g., an LSI (Large Scale Integration) as a load device).
Because regulators are inexpensive and provide a low failure rate, replacing a DC-DC converter with a plurality of regulators may reduce the production costs of a power supply apparatus. In contrast, when a plurality of regulators is used, each output voltage of regulators needs to be regularly monitored because the output voltage is different for each regulator.
For example, Patent Document 1 discloses a power supply monitoring apparatus that reads output voltage of each regulator with an ADC (Analog Digital Converter) and gives out a warning when output voltage is below or above a reference value.
Further, Patent Document 2 discloses a power supply apparatus that monitors a plurality of power supplies and stops a power supply by outputting a signal to shut down the power supply where an error of output voltage is detected.
When a conventional configuration of a power supply monitoring apparatus in which one system monitoring processor (SPV: Service Processor) monitors output voltage by one ADC reading the output voltage of one DC-DC converter is changed into a configuration where one DC-DC converter is replaced by a plurality of regulators, the system-monitoring processor firmware needs to be substantially changed when the conventional technology notably disclosed in Patent Documents 1 or 2 is used. Thus, a problem of incompatibility arises in that the power supply apparatus including a power supply monitoring apparatus ends up incurring rather higher production costs because there is no compatibility with the configuration of a conventional power supply monitoring apparatus.    [Patent Document 1] Japanese Laid-open Patent Publication No. 08-005693    [Patent Document 2] U.S. Pat. No. 6,289,467